THE BAIKAL NEUTRINO EXPERIMENT: STATUS, SELECTED PHYSICS RESULTS, AND PERSPECTIVES Vladimir Aynutdinov, INR RAS, Moscow for the Baikal Collaboration for the Baikal Collaboration VLVnT April 2008

Collaboration  Institute for Nuclear Research, Moscow, Russia.  Irkutsk State University, Russia.  Skobeltsyn Institute of Nuclear Physics MSU, Moscow, Russia.  DESY-Zeuthen, Zeuthen, Germany.  Joint Institute for Nuclear Research, Dubna, Russia.  Nizhny Novgorod State Technical University, Russia.  St.Petersburg State Marine University, Russia.  Kurchatov Institute, Moscow, Russia.

Baikal Outline: Introduction Neutrino telescope NT200 ( ) Design and Physics Results (selected) Future Gigaton-Volume (km3-scale) detector BAIKAL-GVD Preliminary Design NT200 upgrade  NT200+ ( ) Prototype string for BAIKAL-GVD detector (April 2008) Summary

Baikal - History Since 1980 Site tests and early R&D started 1989/90 Proposal NT200 detector in lake Baikal submitted NT NT36 started (36 PMTs at 3 strings) The First Underwater Array First Neutrino Candidates NT200 commissioned NT200 commissioned Start full Physics program NT200+ commissioned NT200+ commissioned /7 R&D for Gigaton (km3-scale) Volume Detector (GVD) 2008 April prototype string for GVD was installed2008 April prototype string for GVD was installed

The Site 4 cables x 4km to shore. 1070m depth 3600 m 1366 m NT-200 Absorption length: ~25m Scattering length: m Detection volume >> geometrical volume

Ice stable for 6-8 weeks/year: –Maintenance & upgrades –Test & installation of new equipment Winches used for deployment

-8 strings: 192 optical modules  96 measuring channels  T, Q measure *Timing ~ 1 nsec *Dyn. Range ~ 10 3 ph.e. Effective area: 1 TeV~2000m² Eff. shower volume: 10TeV~ 0.2Mt Quasar : d = 37cm Height x  = 70m x 40m, V inst =10 5 m 3

Low energy phenomena (muons) - Atmospheric neutrinos High energy phenomena (cascades) Diffuse neutrino flux - Diffuse neutrino flux - Neutrinos from GRB - Prompt muons and neutrinos Search for exotic particles - Magnetic monopoles - WIMP Selected Results

Atmospheric Muon-Neutrinos Skyplot of NT200 neutrino events for 5 years (galactic coordinates) 372 Neutrinos in 1038 Days ( ) 385 events from Monte-Carlo E THR GeV

( Lake Baikal (NT200) & South Pole (Amanda) Complete sky coverage including central parts of Galaxy Lake Baikal South Pole Skyplot of neutrino events Atmospheric Muon-Neutrinos

 +   b + b C +  +  no osc. osc. upward going muons Angular distribution of upward going muons as well as background expectation (502 days) Limits on the excess muon flux from the center of the Earth as a function of WIMP mass Search of nearly vertically upward going muons, exceeding the flux of atmospheric neutrinos WIMP Search 24 ev.

Search for fast monopoles N   = n 2 (g/e) 2 N   =8300 N   (g = 137/2, n = 1.33) ~E  =10 7 GeV Event selection criteria: 1.Hit channel multiplicity N hi t > 35 ch 2. Upward-going monopole  (z i -z)(t i -t)/(  t  z ) > 0.45 &  o Background - atmospheric muons Limit on a flux of relativistic monopoles:  < cm -2 sec -1 sr -1 90% C.L. upper limit on the flux of fast monopole (994 livedays) Amanda II (preliminary)

NT200 large effective volume NT200 is used to watch the volume below for cascades.  („BG“) Search for extraterrestrial high energy neutrinos Look for upward moving light fronts. Signal: isolated cascades from neutrino interactions Background : Bremsshowers from h.e. downward muons

Experimental limits + bounds/ predictions Diffuse Neutrino Flux Limits + Models NT200 (1038 days) no statistically significant excess above the background from atmospheric muons has been observed The 90% C.L. “all flavour” limit (1038 days) for a  =2 spectrum Ф ~ E -2 (20 TeV < E < 50 PeV), and assuming e :  :  = 1  1  1 at Earth ( 1  2  0 at source ) E 2 Ф <8.1·10 -7 GeV cm -2 s -1 sr -1 (Baikal 2006)

Searching for diffuse neutrinos based on cascades reconstruction Energy distribution of experimental (1999), as well as generated and reconstructed events from atmospheric muons Cascade reconstruction:  lgE ~ 10%;  r ~ (5-10)%;  o Selection conditions: E>100 TeV, N hit >18 Cut E>100 TeV old cut Hit channel multiplicity Expected limit (1038 days) for E -2 spectrum: E -2  ~ 4 ·10 -7 GeV cm -2 s -1 sr -1 (twice lower than old one)

Ultimate goal of Baikal Neutrino Project: Gigaton (km3) Volume Detector in Lake Baikal Sparse instrumentation: 91 – 100 strings with 12 – 16 OMs (1300 – 1700 OMs) - effective volume for >100 TeV cascades: ~ km³  lg  E) ~ 0.1,  med  < 5 o - detects muons with energy > TeV 624 m 280m 70m 120m 208m

NT200+ (2005) 36 additional PMTs on 3 far ‘strings‘  4 times better sensitivity  Improve cascade reconstruction Vgeom ~ 4 ·10 6 m 3 Eff. shower volume: 10 4 TeV ~ 10 Mton Expected -sensitivity (3 yrs NT200+) E 2 Ф V < 2 · GeV cm -2 s -1 sr -1 Basic building block of Gigaton Volume Detector - Height = 210m - = 200m -  = 200m - Volume ~ 5 Mton NT200+ = NT outer strings

Calibration and time synchronisation with laser 100m X2 X1 X3 100m  Laser is visible >200m with high Ampl. (NT200 and Ext.strings) Laser intensity : cascade energy: (10 12 – )  : (10 – 500) PeV NT200+ time resolution

NT200+ efficiency of cascade reconstruction Laser coordinates reconstruction NT200 NT extern. str.  r < 1 m (E cascades  10 PeV)

Prototype string km3-scale BAIKAL telescope NT200+ current status Prototype string Installation of a “new technology” prototype string as a part of NT200+ (8 April 2008)  Investigations and in-situ tests of basic elements of km3 detector: optical modules, DAQ system, new cable communications.  Studies of basic DAQ/Triggering approach for the km3-detector.  Confrontation of classical TDC/ADC approach with FADC readout.

Design of Prototype string FADC data are transmitted through an Ethernet line to PC unit String PC connected through DSL-modem to central NT200+ control unit Control of OM and LED flasher through RS-485 underwater bus (coax. cable) 60 m 8-ch 12-bit 200 MHz FADC unit Trigger: - 1…4-fold OM coin. - outer NT200+ trig. OM power supply control Ethernet data line OM signal & power – 1 coax. cable PMT: XP1807 (Photonis, 12”), R8055 (Hamamatsu 13”) HV : PHV12-2.0K DC-DC conv. VIP-2A (Irkutsk) DC-DC OM controller: - microcontroller C8051F124 - RS-485 interface - PM pulse counter - HV control & monitor - 2-LED calibration

Basic parameters of prototype string prototype string Number of optical modules: 6 Number of spectrometrical channels: 8 Type of PMT: XP1807 (12”), R8055 (13”) Dynamic range: high gain chan. 0.2 … ~100 p.e (*) low gain chan. 0.5 … ~300 p.e. Time window: 5 mks Time resolution: < 5 ns (*) – range of spectrometrical channel linearity

String control center: LED flasher FADC unit PC unit

Optical module installation: UP-looking OM DOWN-looking OM

Prototype string in-situ tests (LED flasher) Time shift estimation with LED flasher: time difference between neighbored OMs OM#1 OM#2 OM#3 OM#4 OM#5 OM# ~20 m coax cable ~20 m A, V Example of LED flasher event PRELIMINARY ~20 m coax cable ~20 m

Prototype string in-situ tests (Laser event) OM#1 OM#2 OM#3 OM#4 OM#5 OM#6 50 m LASER Example of laser event with time shift correction PRELIMINARY

Prototype string in-situ tests (muon event) Example of down-going muon event Trigger: 3-fold coincidence OM#1 OM#2 OM#3 OM#4 OM#5 OM# PRELIMINARY ?

CONCLUSION 1. BAIKAL lake experiment is 1. BAIKAL lake experiment is successfully running since The First Underwater Array - First Neutrino Candidates - Some HE neutrino production models already ruled out by the experiments 2. NEW configuration NT200+ starts work at April 2005 and is successfully operating now. - Improved cascade reconstruction - NT200+ gives good possibilities to optimise the design and to investigate the key elements of future Gton scale detector 3. Start R&D for Gigaton Volume (km3-scale) Detector (BAIKAL-GVD) - A “new technology” prototype string was installed: 6 OMs with 12”/13” - Preliminary in-situ tests of the prototype string with underwater laser, LED flasher and muons shows good performance of all string elements.

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Cable communications Time synchronization with NT200+: 2 coaxial cable, Request & Acknowledgment Connection to shore: DSL 2-wire line, 1 Mbit OM slow control: RS-485 bus on the basis of coaxial cable FADC and PC unit connection: Ethernet on the basis 2 coaxial cables OM signal & power supply: individual coaxial cable to each module Time calibration with LED flasher: individual optical fiber to each module

OM#2, low gain channel Examples of laser events for 5 laser intensities I1I2 I3 I4I5 OM#1 OM#2 OM#3 OM#4 OM#5 OM#6 50 m LASER Prototype string in-situ tests Laser RUN: events rate vs. time. 5 laser intensities: I1, I2,…,I5. I i /I i+1 ~ 2.5…3 PRELIMINARY